Synthesis of Well-Defined, Water-Soluble Hyperbranched Polyamides by Chain-Growth Condensation Polymerization of AB2 Monomer

Condensation polymerization of 5-aminoisophthalic acid methyl ester 1 bearing a N-tri(ethylene glycol) methyl ester (TEG) chain as an AB2 monomer was conducted and the properties of the resulting hyperbranched polyamides (HBPA) were investigated. When the polymerization of 1 was carried out with N-methyl core initiator 2b at various feed ratios of 1 to 2b ([1]0/[2b]0) in the presence of LiHMDS and LiCl at −10 °C, the Mn values of the obtained HBPA increased in proportion to the [1]0/[2b]0 ratio from 7 to 46 (Mn = 3810–18600), retaining a narrow molecular weight distribution (Mw/Mn = 1.11–1.19). The HBPA was soluble in water, and a 0.25 wt.−% aqueous solution of the HBPA exhibited a lower critical solution temperature (LCST). The cloud point was 21–23 °C, which is about 30 °C lower than that of the corresponding poly(m-benzamide) with the N-TEG unit